This invention relates to a knee joint prosthesis, and more particularly to a prosthesis useful to augment bone deficiencies during knee arthroplasty procedures.
Knee arthroplasty is a well known surgical procedure by which a diseased and/or damaged natural knee joint is replaced by a prosthetic knee joint. In some instances, due to disease or trauma, insufficient healthy boney mass exists at the distal end of the femur to secure a femoral prostheses. It is thus necessary to remove a portion of the femur to ensure sufficient anchoring and a proper fit for the femoral prosthesis. In these instances, and in other cases, it is necessary to augment the inferior portion of the femoral component of the prosthesis to add additional thickness a prosthesis to compensate for a lack of sufficient boney tissue.
Augmentation of the boney mass can be accomplished by securing augmenting devices to the femoral component. Earlier techniques require that the augmenting devices be cemented to the inferior surface of the femoral component. Such techniques require accurate measurements and a great deal of precision since the augmenting device is difficult, if not impossible, to remove once it is secured to the prosthesis. These techniques do not allow sizing of the proper augmenting device by trial and error.
An improved augmentation technique is described in U.S. Pat. No. 4,936,847 (Manginelli). This patent describes an augmentation system that can be removeably and replaceably secured within a femoral component of a knee joint prosthesis. Such as design is advantageous because it avoids the need to cement augmenting devices to the inferior surface of the femoral component. As a result, augmenting devices of varying thicknesses can be fitted into place on the inferior surface of the femoral component. The augmenting devices can be removed and replaced with devices having different dimensions until the proper augmentation thickness is determined. Such an augmentation system, however, requires a specially constructed femoral component.
Despite existing augmentation systems, there remains a need to provide improved systems that allow standard augmenting components that can easily and securely be affixed within an existing femoral component. The cost of joint prostheses that utilize many current augmentation systems can be quite high due to the scrap rate and because prosthesis components, such as femoral components, must often be specially constructed to accommodate the augmenting devices. There is thus a need for an augmentation system that allows augmenting devices to be easily and securely fitted to standard prosthesis components.
It is thus an object of the invention to provide a femoral augmentation system that securely and easily fits within a femoral component of a knee joint prosthesis. Another object of the invention is to provide a femoral augmentation system that is compatible with standard femoral components of knee joint prostheses. It is also an object to provide an augmentation system that offers a great deal of versatility in that it can be used with different types of femoral components, including cruciate retaining and cruciate sacrificing femoral components. Other objects will be apparent to one of ordinary skill in the art upon reading the description that follows.